Generation And Propagation Of Longitudinal Cracks In Asphalt Pavement Of Widening Projects

Since the 1980s, with the rapid development of national economy, the highway construction has developed rapidly in China, and highways have taken more and more important role in the development of national economy. Meanwhile, the traffic flow is increasing day by day, so that the design traffic capacity of original highway has far not met the increasing traffic demand. Therefore, it is necessary for the original highway to be widened.In recent years, many highways have been widened home and abroad. But longitudinal cracks appeared in the most junctions between the new and old road during the usage period. The reason is that no standards or specifications are offered in China to follow for the design and construction of widening project, mostly depending on experience, and the current study is not clear on the mechanism of generation and propagation of the longitudinal cracks of widening project. Therefore, in order to provide guidance for widening projects, it is necessary to study on issues of the longitudinal cracks systematically.This thesis firstly analyzed the species and reasons of diseases of widening projects qualitatively and then systematically analyzed the generating mechanism and the propagating rule of longitudinal cracks by using ABAQUS finite element software.The research results are obtained as follows.(1)The subgrade finite element model of widening projects was established, and the subgrade deformation of the construction and consolidation periods was simulated, and then the settlement deformation rule of new and old embankment was analyzed. The results showed that“bending basin shape”appeared in the settlement curves of new and old embankment surface with curvature mutations between the new and old junction.(2)The stress characteristics of widening pavement structure under different settlement of embankment was analyzed, and so was the influence factors of additional stress. And also the generating mechanism and the types of longitudinal cracks were expounded. Analysis showed that the most adverse position of widening pavement structure is the top surface of base of the junction, followed by the top surface of the AC layer, and additional flexural stress is the main cause of longitudinal cracks. (3)The propagating rule of longitudinal cracks and influence factors under traffic loads were analyzed, and the fatigue life of transfixion cracks was predicted. The results showed that partial load is the more adverse load, the reflected and surface cracks both express“П”expansion, and it can propagates throughout the AC layer during the usage period.